The main objective in this research project is to study optical reflectance from peripheral tissue in order to obtain theoretical understanding of optical reflectance as a function of tissue hemoglobin oxygen saturation and tissue hemoglobin content. Understandings gained here will be used to design and develop a non-invasive tissue reflectance oximeter for the continuous measurement of hemoglobin oxygen saturation in hemoglobin content in peripheral tissue. In the proposed work, experimental data were obtained relating the measured optical reflectance in the red and near infrared region with tissue hemoglobin oxygen saturation and hemoglobin content. Extensive modelling work was carried out using different simulated as well as real tissue models in order to derive an analytical relationship between measured tissue optical reflectance and the estimated tissue hemoglobin oxygen saturation and hemoglobin content at different wavelengths. Based upon the above experimental results, a prototype tissue reflectance oximeter has been constructed and evaluated using an isolated gut preparation in dogs. Our experimental results today indicate that quantitative estimation of tissue oxygen saturation and hemoglobin content are possible with our current technique with standard errors of approximately 5% as compared with known oxygen saturation from simultaneously drawn blood samples from the experimental preparation. Current efforts are being devoted to the design nd implementation of a rela-time non-invasive tissue reflectance oximeter that might be suitable for clinical applications.